Jurassic Period

Saurischian Dinosaurs

What were the ceratosaurs?

The ceratosaurs (Ceratosauria, or “horned reptiles”) comprise a major theropod division. These were among the earliest theropods, arising during the Triassic period and evolving into much larger animals during the Jurassic period.

Similar to all known theropods, the ceratosaurs had hollow bones—bones that were much stronger and easier to bend than solid ones. The ceratosaur dinosaurs had strongly curved, S-shaped necks, similar to those exhibited by modern birds, but on a much larger scale. (Scientifically, this is expressed by saying the ceratosaurs began to exhibit bird-like features, or more appropriately, birds show ceratosaurian features.)

Another ceratosaur characteristic included its upper jaw bone structure: there was a loose attachment between the two upper jaw bones, known as the premaxilla (a front bone of the upper jaw) and the maxilla (main upper jaw bone, behind the premaxilla). The notch formed by this arrangement was filled by a large tooth in the lower jaw when the mouth was closed.

Allosaurs were a type of tetanuran, which included other carnivores such as velociraptors and the tyrannosaurs (iStock).